Support coils, for the radial support of resiliently expanded tubing material, are readily known in the art, and are used to maintain pre-assembled structure, for example, insulating tubes and socket members in an expanded state before final assembly. Insulating tubes and socket members are used for the electrical insulation or sealing of electrical components in the energy industry, such as cable couplings or cable connectors, for example. Because high voltages of over 100 kV, for example, can be applied to these components, the insulating tubes are developed with thick walls and manufactured from materials that insulate well, such as silicone, for example. Such tubing materials, so-called cold shrink tubing, should resiliently match the outer contours of the component to be insulated and enclose it with no gaps if possible. Therefore, the tubing material is expanded resiliently up to 4 times its diameter before assembly. The electrical and other components can therefore be easily inserted into the tubing material.
In order to keep the tubing material in its expanded state until it is assembled, a supporting body in the form of the above-mentioned support coil is inserted into the tubing material, which absorbs the restoring force of the tubing material that is present due to the resilient expansion. To assemble, the component that is to be enclosed is positioned inside the support coil, which has a hollow interior. Then the support coil must be removed from the tubing material so that the tubing material can shrink around the component.
In order to be able to remove the support coil, which is tightly enclosed by the tubing material, upon which pressing forces of up to 10 bar, for example, can be applied, manually from the tubing material, support coils of the above-mentioned type have proved themselves. This type of support coil can be dismantled in stages in a longitudinal direction by unwinding the extruded profile body, in that the unwound extruded profile body pulled out by the hollow support coil. When the support coil is dismantled in stages in this way the tubing material shrinks around the component to be insulated by itself. In this way, the support coil can be removed manually from the tubing material without further tools or devices.
Consequently, the support coil of the stated type must on one hand be able to constantly withstand high pressure emanating from the expanded tubing material and on the other be manually removable from the tubing material by pulling the extruded profile body out. Furthermore, it is important for the support coil that there is enough overall space available inside the interior of the support coil, due to a wall thickness that is as thin as possible, to insert the component to be enclosed.
In order to fulfill these requirements, the front faces of the wound extruded profile body are connected to each other and joined together in the known support coils in a material-uniting manner, for example, by welding or gluing. The front faces to be connected are also formed so that they link into each other.
Known support coils are described for example in U.S. Pat. No. 5,087,492, EP 0 619 636 A1, WO 93/22816, WO 83/00779, DE 19820634 C1, EP 0399263 A2, U.S. Pat. No. 5,670,223 and WO 96/24977.
Generic support coils, for example U.S. Pat. No. 5,670,223, are based on the principle that the elements of the tongue and groove arrangement or the ratchet arrangement of the adjacent turns that are to be connected to each other are connected to each other frictionally, so that no substantial reduction of the interior space being kept free by the support coil can take place substantially through the resilient restoring force of the expanded tubing material that is being applied from the outside. This requirement, however, is in opposition to the endeavor of manually removing the extruded profile body easily from the tubing material. Whilst for the first issue an intimate connection of adjacent turns is desirable, it is actually a hindrance to the second issue. Furthermore, variations in the dimensional accuracy, particularly of the tongue and groove or ratchet arrangements, lead to a non-uniform connection. The releasing forces needed for the manual unwinding of the extruded profile body can sometimes vary greatly due to these non-uniform connections, so that the separation of the connected front faces can be made more difficult or manually impossible when the support coil is being dismantled, or the tubular support coil can fail and break under the pressure of the resiliently expanded tubing material. On the other hand, the support coil must also reliably take up the high restoring forces of the expanded tubing material without this making the removal of the support coil more difficult or even impossible in the process.